1. Field of the Invention
The present invention relates to a hydraulic actuator for automobiles for engaging and disengaging an automatic clutch.
2. Prior Art
Automatic clutches are used in automobiles having automatic transmissions. One example of such automatic clutches is disclosed in Japanese Patent Laid-open Publication No. 60-60334. The disclosed automatic clutch is controlled by an hydraulic actuator which includes a plurality of solenoid valves properly operated by control signals from an electric control unit for reciprocating the piston of a hydraulic cylinder to actuate a clutch release lever connected to a piston rod, thereby disengaging and engaging the clutch.
The electric control unit for operating the hydraulic actuator is constituted by a microcomputer which is used also for the control of engine operation. For purposes of safety, the microcomputer is disposed at a suitable position in the passenger compartment. With this placement, extending between the microcomputer and the hydraulic actuator of the automatic clutch which is disposed in an engine room are a number of cables for the passage of driving currents. In addition thereto, cables are necessary for obtaining detecting signals from a position sensor provided for detecting the clutch position. Thus, the prior art system requires a large number of cables extending between the passenger compartment and the engine room for electrically connecting the microcomputer and the hydraulic actuator.
The electric control unit or microcomputer, as described above, is commonly used for the control of engine operation and the control of hydraulic actuator and hence is so programmed as to perform both operation controls. With an increased employment of the hydraulic actuators in view, it is desirable to use the same type of hydraulic actuator in different types of automobiles, however, this requires program modification of electric control unit to suit with the corresponding type of automobile. Accordingly, the corresponding number of types of electric control units are required and the compatible use of the actuators is difficult to achieve. Furthermore, the common use of the electric control unit for controlling several different apparatus would result in overloading of the electric control unit.